Motor fuel production



Nov'- 14. 1939. c. AhMisTEAD, JR

MOTOR FUEL PRODUCTION Filed OCT.. 25. 1937 ATTORNEY Patented Nov. 14, 1939 UNITEDy STATES PATENT OFFICE MOTOR FUEL PRODUCTION Application October 23, 1937, Serial No. 170,601

3 Claims.

This invention relates to the treatment of hydrocarbon oils to produce therefrom lighter hydrocarbon oils including motor fuel. More particularly, the invention relates to the treatment 5 of a plurality of hydrocarbon oils of differing boiling ranges to produce therefrom motor fuel of high anti-knock value under conditions of highest efliciency. More particularly, the invention relates to the treatment of crude oil or partially topped crude oil to effect conversion thereof to motor fuel of high anti-knock value under conditions of highest eiciency.

It is an object of the invention to provide a method of treating a plurality of hydrocarbon oils of differing boiling ranges wherein said hydrocarbon oils, and intermediate products produced therefrom, are treated under conditions selected for each oil to produce motor-fuel products, and intermediate products suitable for further conversion, to effect a combined operation of highest eciency whereby motor fuel of high anti-knock value is produced with minimum production of gas and undesirable products and with a minimum requirement in apparatus.

It is a further object of the invention to provide a method of converting crude oil or partially topped crude oil into motor fuel of high anti-knock value under the conditions outlined above. Y

The invention contemplates the treatment of a light hydrocarbon oil, which advantageously is a heavy naphtha condensate produced by distillation of crude oil, to effect conversion of the light oil to motor fuel of high anti-knock value, for example, by passage through a suitable pipe coil in a heating furnace. A heavy hydrocarbon oil, which advantageously is a heavy condensate or reduced crude vfrom the distillation of crude oil, is admixed with said light hydrocarbon oil, or heavy naphtha which has been subjected to reforming conditions of temperature and pressure, whereby the heavy hydrocarbon oil, for example, reduced crude, is subjected in admixture with the reformed heavy naphtha to cracking conditions which are relatively drastic for said reduced crude t effect conversion of the reduced crude to lighter products including a substantial proportion of constituents above the motor-fuel boiling range and including motor-fuel constituents of high anti-knock value. This operation may be performed conveniently by introducing the reduced crude into the pipe coil in which the heavy naphtha is being reformed at an intermediate point or points spaced from the inlet of the pipe coil whereby the heavy naphtha is subjected to substantial refo-rmingprior to admixture with a reduced crude. The resulting mixture is .passed through the remainder of the pipecoil to effect ythe desired cracking of the reduced crude and any desired further reforming of the heavy naphtha. The introduction of the reduced crude into the pipe coil may be arranged whereby the resulting mixture of reduced crude and naphtha thereafter passes through a portion of the coil located in a relatively cool part of the furnace which may act as a soaking section for the naphtha as Well as a cracking zone for the reduced crude. The relatively drastic cracking of the reduced crude in the presence of the naphtha undergoing reforming reactions permits the production of motor-fuel constituents directly from the reduced crude under conditions whereby the normal tendency of the reduced crude to deposit coke is offset by the presence of the large volume of gases resulting from the reforming treatment of the naphtha and under conditions whereby constituents resulting from the cracking of the reduced crude may be combined directly with constituents formed by the reforming reactions of the heavy naphtha, with the production of additional quantities of motor-fuel constituents of high anti-knock value and a reduction in the gas loss from the reforming of the naphtha. This permits the production of gasoline constituents directly from the reduced crude of higher antiknock value than is possible Where reduced crude is cracked alone under conditions to prevent excessive coke formation. y .c

The products of the combined reforming treatment of the heavy naphtha and cracking treatment of the reduced crude are separated under pressure into vapors and liquid residue, and the resulting vapors `are fractionated to separate therefrom a heavy gas-oil reflux condensate.

A clean hydrocarbon oilintermediate inboiling range between the said light hydrocarbon oil and said heavy hydrocarbon oil, and Which advantageously is a virgin gas-oil condensate obtained in the above-mentioned crude oil distillation, is subjected to cracking conditions of temperature and pressure to effect conversion to lighter products including motor-fuel constituents. The virgin gas oil may be subjected to this treatment alone or in combination with cycle gas oil from the system. This cracking treatment may advantageously be carried out by passing the said virgin gas oil through a suitable pipe coil in a heating furnace. The cracked virgin gas oil is admixed with heavy gas-oil condensate obtained as described above, and the resulting I.

mixture is subjected to cracking conditions Whereby the said heavy gas oil is converted to lighter products including a substantial proportion of constituents above the motor-fuel boiling range and said virgin gas oil is subjected to any desired further cracking treatment. For example, this step advantageously may be carried out by introducing the heavy gas-oil condensate into the pipe coil in which the virgin gas oil is undergoing cracking treatment at an intermediate point or points spaced from the inlet of said pipe coil whereby the virgin gas oil is subjected to substantial cracking treatment prior to admixture with the heavy gas-oil condensate thus introduced. The resulting mixture then passes through the remainder of the pipe coil wherein the desired cracking of the heavy gas-oil condensate is effected with further cracking of the virgin gas oil as desired. Conveniently, the portion of the pipe coil through which the mixed products pass may be located in a cooler portion of the furnace whereby it constitutes a soaking section in the cracking of a virgin gas oil and a cracking section for the heavy gas-oil condensate.

The products of the cracking of the virgin gas-oil condensate and any accompanying cycle gas oil and the cracking of the heavy gas-oil condensate are separated into vapors and liquid residue, and the vapors may be fractionated to separate therefrom a heavy gas-oil reux condensate, a lower-boiling gas-oil reflux condensate and naphtha distillate. The naphtha distillate may be further fractionated to separate therefrom a heavy naphtha condensate which may be combined with heavy naphtha from the distillation of the reduced crude for processing therewith.

The vapors separated from the products of the combined reforming of the heavy naphtha and cracking of the reduced crude may be further fractionated after the separation therefrom of the heavy gas-oil reux condensate to separate therefrom a lower-boiling gas-oil reflux condensate and a naphtha distillate.

The fractionation of the vapors from the said cracking treatments may be accomplished in separate Zones, or the vapors may be combined for fractionation. The preliminary separation of the cracked products is preferably accomplished in separate Zones whereby the fuel oils produced may be handled separately. For example, the cracked products from the combined reforming and cracking treatment may be separated in a separate zone and the resulting vapors passed to a fractionating zone. The cracked products from the combined cracking of the virgin gas oil and heavy gas-oil reflux condensate may be introduced directly into the lower portion of the said fractionating zone, and the vapors separated therein are fractionated in the upper portion of said zone together with vapors from the other cracking treatment. The lowerboiling gas oil may be returned for cracking on a recycling basis with the said virgin gas oil, or the virgin gas oil produced as described may be cracked in a separate zone on a once-through basis while other lower-boiling gas oils produced in the system from the cracking of the reduced crude and the heavy gas oil reflux condensate may be further treated by separate cracking means.

A portion of the heavy gas-oil condensate produced in the system may be diverted and combined with the reduced crude for processing therewith.

The accompanying drawing is a ow diagram of apparatus suitable for carrying out the present invention. The invention will be described in more detail with reference to the drawing, but it is to be understood that the invention is not to be limited by such reference but is capable of other modifications which may be beyond the physical limitations of the apparatus indicated.

Crude oil or partially topped crude oil is introduced into the system through line l provided with a pump 2. The crude oil may be heated by any desired means, such as heat exchange with hot gases or vapors produced in the system, cr the oil may be preliminarily heated partially by such means and raised to the final temperature desired by passage through a coil located in the relatively cool part of a cracking furnace, or such coil may be separately heated, or the crude oil may be heated entirely by passage through such a heated coil. For purposes of illustration and without intending to limit the invention thereby a separate heater 3 provided with a suitable heating coil to which line l connects is indicated. In heater 3 the crude oil or partially topped crude oil is heated to a distillation temperature which will depend on the extent of distillation desired and the nature of the charge. Generally speaking, the oil may be heated to a temperature of 500 to 800 F. under a pressure from atmospheric to pounds per square inch. The heated oil is withdrawn from heater 3 through line ll which is provided with a valve 5 to effect any desired reduction in pressure. Line 4 connects with the lower portion of a crude ash tower 6 wherein separation of vapors and reduced crude is eifected. The reduced crude descends to the bottom of the tower G, and the heating of the crude oil under conditions maintained in tower 6 is regulated to effect vaporization of the majority of constituents boiling below 55C-650 whereby the crude oil or partially topped crude oil which may have had an original gravity of 35 to 40 A. P. I. is distilled to leave a reduced crude having a gravity of 20 to 25 A. P. I. Auxiliary heating means 'l may be provided in the bottom of the tower 6 to secure the desired distillation, if necessary.

Conditions of temperature and pressure are maintained in tower 6 to effect condensation of a part of the vapors whereby the vapors leaving its top consist of a light naphtha distillate and lighter constituents. For example, the tower may be maintained at a pressure from atmospheric to 25 pounds per square inch with a bottom temperature of 500 to 650 F. and a top temperature of 250 to 350 F. Any suitable means such as liquid reflux or a cooling coil may be provided in the upper portion of tower 6 to effect maintenance of the desired temperature at that point. For example, a cooling coil 8 may be employed. Trap-out trays 9 and I0 are provided at suitable intervals above the point of introduction of the heated crude to collect from the liquids condensed from the vapors a heavy naphtha condensate and a virgin light gas oil condensate, respectively. For example, the heavy naphtha condensate may be one having an initial boiling point of to 300 F. and an end point of 400 to 500 F. The virgin gas-oil condensate may have an initial boiling point of 400 to 500 F. and an end point of approximately 650 F.

The heavy naphtha condensate is withdrawn .from trapout tray 9 through line II provided with a valve I2 by means of pump I3 located in line II. Line II connects with the coil of the reforming heater I4. For purposes of convenience reforming heater I4 is shown as a separate heat-l It is to be understood that this is for purposes of ilustration, however, without intending to limit the invention to that arrangement. The function of heater I4 may be equally well performed by a coil located suitably in a furnace which also serves to heat one or more other coils through which different liquids are passed. In heater I 4 the heavy naphtha passed therethrough is heated to a temperature of 900 to l050 F. at a pressure to 200 to .1000 pounds per square inch to effect cracking ofthe naphtha with accompanying polymerization and other conversion reactions to effect the production of a reformed naphtha having improved anti-knock properties.

Reduced crude is withdrawn from the bottom of tower 6 through line I5 provided with a valve Iii by means of pump I'I located in line I5. Line I5 connects with the coil of heater I4 at an intermediate point or points therein whereby the reduced crude withdrawn from tower through line l5 is introduced into the coil of heater I4 and admixed with the heavy naphtha passing therethrough which has been previously heated t'o the above-mentioned cracking temperature. Conveniently, the coil of heater I 4 may be arranged in the furnace and the point of introduction of the reduced crude selected whereby the resulting mixture of reduced crude and heavy naphtha thereafter passes through a portion of the coil located in a portion of the furnace where somewhat lower heat transfer rates are employed whereby the said portionA of the coil constitutes a soaking section in the cracking of the heavy naphtha which servesy to substantially crack the reduced crude and where conditions are appropriate for the polymerization of certain of the normally gaseous hydrocarbon products of the reforming and also for their reaction with the heavier hydrocarbons through alkylation and similar reactions to produce hydrocarbons of the motor fuel boiling range, or which can becracked to this boiling range in subsequent stages of the system. For example, the proportion of reduced crude added and its temperature may be controlled to effect a reduction of temperature in the coil in the said soaking section to a temperature of 850 to 975 F. The reduced crude y withdrawn from tower 6 is ordinarily at a temperature of 500 to '700 F. The adjustment of this temperature prior to introduction into the coil of heater 0 to control the degree to which the heavy naphtha is cooled may be effectedby either heating or cooling the reduced crude in suitable heat exchange not shown. The portion of the coil through which the mixture of reduced crude and heavy naphtha passes may be maintained at the same temperature as the remainder of the coil, or any desired reduction in pressure may be effected at any point in the section through which they pass. v

The cracked products from heater I4 are withdrawn therefrom through line I8 provided with a valve I 9 to effect any desired reduction in pressure. The line I8 connects with a separator 20 which may be maintained at or below the pressure in the heater I4, but preferably the pressure is somewhat lower than that of the heater |4 whereby separation of vapors and liquid residue is effected to produce vapors containing the desired constituents and/or a fuel oil of desired proper- '3 ties. The'temperature of the constituents in the separator may be 700 to 850 The liquid residue separatedin separator 28- is withdrawn therefrom through line 2| for use elsewhere, for

example, as fuel or for further treatment to recover valuable constituents therefrom. The vapors separated in separator 20 are withdrawn therefrom through line 22 provided with a valve y23 toieffect any desired reduction in pressure.

Line 22 connects with the lower portion of a fractionating tower 24 for introduction of the vapors therein. However, all or a portion of these vapors .may be diverted from line 22 before introduction into tower 24 by means of line 25 which connects with the lower portion of a separate fractionating tower 2B for introduction of vapors therein.

Preferably, the evaporation of the cracked products from heater I4 yin separator 2011s controlled to effect the production of vapors containing products boiling above 650 to 750 F. whereby constituents of heavy gas oil are contained therein. Conditions of operation of towers 24 and 26 are controlled to effect fractionation and condensation of a portion of the vapors whereby the vapors passing overhead contain gas i? voil and lighter constituents.

For example, these towers may be operated at pressures of 25 to 250 pounds per square inch with a top temperature of 650 to 809 F. Any suitable cooling means may be provided in the upper portions of towers 24 `and 20 -such as direct reflux or cooling coils to effect the desired control of temperature thereprovided with a valve 32 by means of a pump 33" located in line 3|. Line 3| connects with the end of a coil of a cracking heater 34. As in the case of heater I4, heater 34 is indicated as a separate heater for purposes of illustration only.

Heater 34 may preferably comprise a coil located in a suitable part of a furnace serving to house other heating coils, for example, that of heater I4. In heater 34 the gas oil introduced through line 3| is heated under elevated temperature and oil whereby substantial conversion of the gas oil to gasoline constituents is eifected. For example, the oil may be heated at a temperature of 900 to 1075 F. at 200 to 1000 pounds per square inch pressure to effect a 25% to 35% conversion to gasoline in the cracked products.

Heavy gas-oil rei-lux condensate collected in trap-out tray 29 of tower 24 may be withdrawn therefrom through line 35 by means of pump 36` located therein. Line 35 connects with the coil of heater34 at an intermediate point or points therein whereby the heavy gas oil passing therethrough after being preheated if desired is introduced into the coil into intimate admixture with the lower-boiling gas oil which has been raised to the above-mentioned cracking. conditions. Preferably the coil of heater 34 is arranged and the point or points of introduction of the heavy gas oil are selected whereby the resulting mixture passes through a portion of the said coil located in a part of the furnace or heater employing somewhat lower heat transfer rates, whereby the y said portion constitutes a soaking section in the .cracking Yof the lower-boiling `gas roil while servpressure to effect substantial cracking of the gasing to effect cracking and conversion of the heavy gas oil to lighter products including a substantial proportion of gasoline and products above the gasoline boiling range. The proportion of heavy gas oil introduced, its temperature and the heat applied to that portion of the coil containing the mixture in the heater 34 are regulated to effect the desired soaking of the lowerboiling gas oil undergoing cracking and the desired cracking of the heavy gas oil. For example, that portion of the coil containing the mixture of gas oils undergoing cracking may be maintained at a temperature of 800 to 975 F. and may be maintained at the same pressure as the remainder of the coil, or a reduction in pressure may be eiected.

The heavy gas-oil fraction collected in trapout tray I30 of tower 26 may be withdrawn therefrom through line 31 which connects with line 35 whereby the heavy gas oil so withdrawn may be introduced into the coil of heater 34 instead of or in addition to the heavy gas oil collected in trap-out tray 29 in the manner described.

A portion of the heavy gas oil withdrawn from trap-out tray 29 through line 35 may be diverted through line 38 which connects with line I5 whereby the said portion of heavy gas oil is mixed with the reduced crude passing through line I5 and introduced into the coil of heater I4 together with the said reduced crude for conversion in the manner described in connection with the operation of heater I4.

Similarly, line 39 connecting lines 3'I and 38 is provided to divert heavy gas oil from line 3l for admixture with the reduced crude in line i5. Valves 4U, 4I, 42 and 43 are provided in lines 38, 39, 3l and 35, respectively, to effect any desired distribution of the heavy gas oil withdrawn from trap-out trays 29 and 36 between the coil of heater 34 and line I5.

The cracked products from heater 34 are discharged therefrom through line 44 which is provided with a valve 45 to maintain any desired back pressure on the coils. Line 44 connects with the lower portion of tower 24 whereby the cracked products are introduced into tower 24 after any desired cooling by heating means not shown. In the lower portion of tower 24 separation of the cracked products from line 44 into vapors and liquid residue is effected. Preferably, a substantial proportion of the cracked products is vaporized whereby the vapors contain heavy gas-oil constituents as well as lighter products. For example, a temperature of '700 to 850 F. is maintained in the lower portion of tower 24 to effect the desired separation. The vapors separated in the lower portion of tower Z4 pass overhead together with any vapors introduced through line 22 and are fractionated for the separation of a heavy gas-oil fraction and the passage overhead of a gas-oil distillate in the manner described above. The liquid residue collects in the bottom of the tower 24 and is withdrawn therefrom through line 4l for use as fuel or for further treatment for the recovery of valuable constituents therefrom.

The vapors uncondensed in tower 24 pass therefrom through line 48. Line 48 connects with a fractionating tower 50 at an intermediate point therein whereby the vapors withdrawn from tower 24 are introduced into fractionator 50 for treatment therein. In fractionating tower 50 conditions of temperature and pressure may be maintained to effect the condensation and collection in the bottom thereof of a reflux condensate and the passage overhead of a naphtha distillate. To this end a bottom temperature of 550 to '750 F. may be maintained with a top temperature of 300 to 450 F. Suitable cooling means may be provided to eiect the desired control as, for example, by cooling coil 52. The tower may be maintained at a pressure of 25 to 250 pounds per square inch, for example. A trap-out tray 53 may be provided at a suitable intermediate point in tower 50 for the collection of a heavy naphtha reflux condensate. The heavy naphtha so collected may be withdrawn through line 54 which connects with line II for combining the heavy naphtha with that from tower G for passage through reforming heater I4.

The condensate collected in the bottom of tower 50 is withdrawn therefrom through line 55 for suitable treatment for the production of valuab-le products therefrom. For example, all or a portion thereof may be diverted from line 55 through line 56 which connects with line 3| whereby the said condensate may be treated in cracking heater 34 in place of or in combination with the virgin gas oil from tower 6.

As described above, tower 26 is operated to effect the separation overhead of vapors consisting of gas-oil constituents and lighter products and the collection of a heavy gas-oil fraction in trap-out tray 30. Condensate collecting in the bottom of tower 26 may be withdrawn therefrom through line 5l for treatment elsewhere for the recovery of valuable products therefrom or for use as fuel. However, since relatively clean vapors only are introduced into tower 26 the condensate collected in the bottom of tower 26 may constitute heavy gas oil of the desired properties whereby it may be used in place of that collected in the trap-out tray 30 whereby trap-out tray 3D may be dispensed with, or heavy gas oil collected at both points may be used in combination. Line 58 connecting lines 5'I and 3'I is provided to effect diversion of heavy gas oil for this purpose.

The vapors uncondensed in tower 26 pass overhead through line 60 which connects with the separate fractionating tower 6I whereby the said vapors are introduced into the fractionating tower 6I for treatment therein. Tower 6I is operated under conditions of temperature and pressure to fractionate from the vapors a condensate which collects in the bottom of the tower 6I and a naphtha distillate consisting of gasoline constituents and lighter products. For example, tower 6I may be operated at a pressure of 25 to 250 pounds per square inch with a top temperature of 300 to 400 F. and a bottom temperature of 500 to 750 F. Cooling means 63 may be provided in the top of tower 6I to assist in maintaining the desired temperature control. The condensate collected in the bottom of tower 6I may be withdrawn therefrom through line 64 for treatment elsewhere for the recovery of valuable products therefrom. If desired, all or a portion may be returned for treatment in the system. For example, line 65 connecting lines 64 and 56 may be provided to divert such condensate for passage through cracking heater 34.

Instead of passing the vapors from tower 26 to fractionating tower 6I all or a portion thereof may be diverted through line 66 which connects lines 60 and fractionating tower 50 whereby the vapors are introduced into fractionating tower 56 for treatment therein together with vapors introduced through line 48.

The vapors uncondensed in towers 6, 50 and 6I head through lines 16, 11 and 18, respectively.

Thev gasolines may be withdrawn separately through lines 19, and 8l for further treatment, or all or a portion of each may be withdrawn through lines 82, 83 and 84, respectively, which connect with a common line by means of which blending of the gasolines in any desired proportions may be effected. Suitable valves are provided to effect the desired distribution of the gasolines. f

' 'Other means not shown may be provided for withdrawing from the system any desired portion of any fuel oil, reduced crude, heavy gas oil, light gas oil or heavy naphtha from the system for treatment elsewhere, it being understood that the proportions of these intermediate products employed in the system for further treatment may be regulated as desired to effect control of the operation of the process of the invention. It is'to be understood that the invention is not to be limited by the fact that the means for collection and withdrawal of the various intermediate products is limited to means for conveying them for further treatment in the system since the drawing has been limited to the illustration of such means in the interests of simplicity of presentation of the subject matter of the invention.

Towers 6, 24, 50, 26 and 6I are suitably provided with trays, bubble caps and other suitable gas and liquid contact means to effect the evaporation, stripping, condensation and absorption incidental to the desired fractionation of the vapors passing therethrough.

The apparatus indicated provides for the sepa- 4ration of the crude oil into reduced crude, a light gas-oil fraction', and a heavy naphtha fraction and the introduction of the reduced crude into the coil of the reforming heater. The invention is not limited to this'method of operation, however, inasmuch as the distillation of the crude oil can be carried to a further step to produce vapors from which a heavy gas-oil fraction may be separated, leaving a fuel oil residue. The heavy gasoil fraction separated `from the products of distillation of the crude oil may then be introduced into the reforming heater in the manner described in connection with thetreatment of the reduced-crude.y

According to a vpreferred method of operation of the presentinvention the heavy naphtha frac'- tion from trap-out tray 9 is passed through the coil of heater I4 to effect reforming treatment of the heavy naphtha to improve its antiknock value. The reduced crude or other heavy fraction from the distillation of the crude oil is introduced into the coil of the'heater I4 at an intermediate point therein to effect cracking of the heavy oil in the presence of the'heavy naphtha during thenal stages of the passage of the heavy naphtha through the coil of heater I4 and to simultaneously bring about polymerization as well as alkylation and other reactions between the` gaseous vhydrocarbon products of cracking and the heavier hydrocarbons present. The resulting products from heater I4 are separated in separator 2,6 into vapors and a,v fuel-oil residue,

and the vapors are introduced through' line 22 into tower 24 for fractionation therein, the operation of separator 20 being controlled to effect inclusion in the vapors of heavy gas-oil constituents.

Vapors introduced into tower 24 are fractionated to separate therefrom a heavy gas-oil fraction which collects in trap-out tray 29.

The virgin gas-oil condensate collected in trapout tray I is withdrawn therefrom and passed through cracking heater 34 to effect drastic cracking of the gas oil with maximum conversion to gasoline constituents. Heavy gas oil from trapout tray 29 is passed through line 35 into the coil of furnace 34 at an intermediate point therein whereby it is intimately contacted with the lower-boiling gas oil which has been subjected to cracking conditions whereby the heavy gas oil is cracked to lighter products in the presence of the lower-boiling gas oil undergoing cracking.

The cracked products from heater 34 are passed through line 44 and introduced into the lower part of tower 24. In tower 24 separation of the vapors and liquid residue is effected, and the conditions of such separation are controlled to effect inclusion in the vapors of heavy gas-oil constituents. The vapors so separated are commingled with the vapors introduced through line 22 and passed upwardly through tower 24 for fractionation in the manner described.

Vapors uncondensed in tower 24 and consisting of light gas-oil constituents and lighter products pass therefrom through line 48 and are introduced into ytower 50 wherein they are fractionated to separate a condensate which collects in the bottom of the tower and `naphtha vapors. The naphtha vapors may be further fractionated to separate therefrom a heavy naphtha condensate which collects in trap-out tray 53, which heavy naphtha condensate may be combined through line 54 with the similar product from tower 6.

The light naphtha vapors uncondensed in tower 6 and the vapors, which constitute a gasoline fraction uncondensed in tower 50, are passed overhead through condensers 10 and 1I, respectively, and collected after separation of noncon-r densibles in collectors 13 and 14, respectively. These gasolines may be separately handled *or may be blended in any desired proportion by means of line 65.

As a modification of the method of operation outlined above, the condensate collected in thev bottom of tower 50 may be withdrawn through lines 55 and 56 and combined with the virgin gas oil in line 3l for cracking treatment in the cracking heater 34. As a further modification, gas oil passing through line 56 may constitute the entire charge to the heater 34, the virgin gas oil from trap-out tray I0 being withdrawn by separate means not shown for treatment 'other passed through line 60 for introduction into separate fractionating towers 6I wherein they 'are fractionated into a naphtha distillate and a gasoil condensate. Thenaphtha distillate sov separated is the product of the high-temperature, high-pressure treatment of the liquids passed through heater lll and may be of relatively high anti-knock value and not need reforming. Therefore, it can be withdrawn overhead through line 69, passed through condenser 'l2 and the resulting condensate separated from uncondensibles in collector l5. The resulting gasoline may be separately withdrawn from collector 'E5 or may be blended with other gasoline produced in the system by means of line 85. Under this method of operation the condensate collected in the bottom of tower Bl may be withdrawn for separate treatment or may be passed through lines S5 and 5B for cracking treatment in` heater 34.

If desired, however, the vapors from tower 2G may be introduced by means of line Gt into tower 50 for fractionation therein jointly with the vapors introduced through line 4S.

The lower-boiling gas oil cracked by passage through heater may consist of virgin gas oil from trap-out tray Ill, reflux condensate from tower 50 or a similar product from tower 6l or may consist of any desired combination from these sources.

The cracking of the heavy fraction from the distillation of crude oil by introduction into the coil of a reforming heater permits the relatively drastic treatment of a heavy cut of relatively great coke-forming tendency in the presence of a relatively large proportion of gas whereby sube stantial conversion of the heavy products to high anti-knock gasoline constituents is effected and whereby the combination of constituents formed by cracking of the heavy material may combine with gaseous constituents formed by the cracking of the heavy naphtha by polymerization and related reactions to effect the production of additional quantities of gasoline and heavier constituents.

By this method of operation the formation of gas by the reforming treatment is reduced as is the production of gas which would follow the similar treatment of the heavy oil in the absence of the cracked heavy naphtha, and the production and deposition of coke is minimized.

The separate collection of fuel oil from the cracked products from the reforming treatment and from the cracked products from the virgin gas-oil cracking treatment permits the separate handling of the fuel oils and greater flexibility in the production of fuel oils of desired characteristics.

The cracking of the heavy gas oil by introduction into the lower-boiling gas-oil cracking coil permits the cracking of the heavy gas oil under relatively drastic cracking conditions in the soaking stage of the cracking of the lower-boiling gas oil whereby maximum conversion of the gas oil to lighter products including gasoline of high anti-knock value is effected.

It will thus be seen. that the present invention provides a method for the treatment of crude or reduced crude wherein said oil is separated into various fractions, and each fraction, and each intermediate fraction produced therefrom, is treated under conditions of maximum efficiency to effect maximum conversion of the crude oil to motor fuel of high anti-knock value with minimum production of gas formation and deposition of coke. The invention also provides a method of great flexibility wherein the conditions of treatment may be varied to provide various operating cycles as required by the nature of the product desired and the nature of the oil undergoing treatment.

These and other advantages are evident from the foregoing description of the invention which has been illustrated by reference to specific modifications. It is to be understood, however, that the invention is not limited by such modifications or embodiments but is capable of other embodiments within the scope of the invention.'

I claim:

l. The method of treating hydrocarbon oils to produce therefrom lower boiling hydrocarbon oils including motor fuel oil which comprises distilling crude petroleum to separate therefrom a crude residuum, a gas oil condensate and a naphtha condensate comprising gasoline constituents, passing said naphtha condensate to an elongated cracking zone of restricted cross-section while applying heat to said elongated heating Zone to subject the naphtha to cracking conditions of temperature and pressure adequate to effect conversion into motor fuel constituents of high anti-knock value, introducing said crude residuum to said elongated cracking zone intermediate the ends thereof into admixture with the naphtha after it has been subjected to substantial conversion therein whereby said crude residuum is raised to a cracking temperature to thereby effect conversion thereof to lighter products during the passage of the admixed hydrocarbons through the remainder of said elongated cracking Zone, separating resultant cracked products from said elongated cracking zone into vapors and residue, fractionating resultant separated vapors to separate therefrom a heavy gas oil condensate and a desired distillate, directing gas oil condensate from the crude distillation t0 a second elongated cracking Zone of restricted cross-section while applying heat thereto to subject the condensate to cracking conditions of temperature and pressure to effect cracking thereof into lighter products including motor fuel' constituents, introducing aforesaid heavy gas oil condensate into the second elongated cracking zone intermediate the ends thereof and into admixture with the condensate therein, after the latter has been raised to a cracking temperature and subjected to substantial cracking, to thereby subject said heavy gas oil condensate to cracking conditions to effect conversion thereof into lighter products during the passage of the admiXed hydrocarbons through the remainder of the second elongated cracking zone, and fractionating resultant cracked products from the second elongated cracking zone to f residuum to said elongated cracking zone inter- F mediate the ends thereof into admixture with the naphtha after it has been subjected to substantial conversion therein whereby said crude residuum is raised to a cracking temperature to thereby effect conversion thereof to lighter products duringthe passage of the admixed hydrocarbons through the remainderof said elongated cracking zone, separating resultant cracked products from said elongated cracking zone into vapors and residue, directing gas oil condensate from the crude distillation to a second elongated cracking zone of restricted cross-section While applying heat thereto to subject the condensate to cracking conditions of temperature and presucts including motor fuel constituents, introducing heavy gas oil condensate formed as hereinafter specified into the second elongated cracking zone intermediate the ends thereof and into admixture with the condensate therein, after the latter has been raised to a cracking temperature and subjected to substantial cracking, to thereby subject said heavy gas oil condensate to cracking conditions to effect conversion thereof into lighter products during the passage of the admixed hydrocarbons through the remainder of the secy ond elongated cracking zone, separating resultant cracked products from the second elongated cracking zone into vapors and residue, fractionating resultant separated vapors from the cracked products of both of said elongated cracking zones in a common fractionating zone to form a heavy gas oil condensate and a desired distillate and utilizing said heavy gas oil condensate as the heavy gas oil condensate introduced into the second elongated cracking zone as aforesaid.

3. The method in accordance with claim 2 wherein the vapors in said common fractionating Zone are fractionated to form in addition to said heavy gas oil condensate and desired distillate an intermediate `condensate and in which said intermediate condensate is combined With said gas oil condensate from the crude distillation for passage through the second elongated cracking zone.

GEORGE ARMISTEAD, JR. 

